<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        var a=parseInt('abc');
        var b=parseInt('def');
        //alert(a==b);//false
 //NaN和NaN不相等
        alert(isNaN(a));//判断是不是NaN
    </script>
</head>
<body>

</body>
</html>